Luigi Gioia ( The Theological Epistemology of Augustine’s De Trinitate ) explains the inseparability of intellect and will in Augustine’s epistemology: “something is recorded by our sensorial activity; this sensation awakens in us a desire to know its cause and to appreciate its value; this desire drives us to turn the sight of our mind to the reasons and standards so that they might enable us to define and evaluate the object known; at this point, if the definition of revaluation pleases us to the point of converting our initial eagerness into full-blown love, we conceive a word (knowledge with love); this love, however, will not be satisfied until it is united to the thing known or possesses it ( copulatio ): only then the word is not only ‘conceive,’ but really ‘born.’”
As Gioia says, this is the furthest thing possible from a “cold, detached, controlled” notion of intellect. Rather, “there is no inquisitio which is not driven by a form of eagerness or desire.” Knowledge “entails union or rather copulation.” The “sexual overtones” of Augustine’s account of knowledge betray “a strong affinity with that of the Old Testament, where the verb ‘to know’ is used to indicate both epistemological and sexual activity.”
Augustine understood, better than we, why the Song of Songs ended up with the wisdom literature.